The bottlenose dolphin is an excellent example of how social alliances can benefit the fitness of individuals. Both direct and indirect fitness benefits are derived from social alliances which males use to acquire mates, dolphins use to gather food, and females or others use for defense. The direct fitness is derived from the improved opportunity for mates, food, or protection, but because certain members of the group get a disproportionate amount of these resources, related individuals are often allied to allow for indirect fitness benefits in which a relative is benefitted by additional resources. The specific dynamics of the dolphin alliances shed light on how and why they are evolutionarily advantageous while also providing interesting insight into the daily lives of these complex organisms.
Discussion questions
What are some factors that may have allowed the specific types of alliances in dolphins to be selected for?
How does kin selection by dolphins satisfy Hamilton’s Rule?
Glossary
Affiliative interaction - interactions that occur to increase a sense of bonding among members of a group, such as contact swimming, petting, or rubbing in dolphins
Consort - (n) a spouse or companion; (v) to habitually associate with
Conspecificity - organisms that belong to the same species
Equivalence rule - a theory that animals group things into classes of equivalent value and treat all members of a certain class as interchangeable
Estrus - a period of time when females are sexually receptive and fecund
First-order alliance - an alliance consisting of two or three males working together to consort a single female
Fission-fusion grouping pattern - a form of social organization in which a large social group partitions into subgroups that change size and composition often
Haplotype - alleles at multiple loci transmitted together on the same chromosome
Kin selection (Hamilton’s rule) - Genes should increase in frequency when rB>C, where r is the genetic relatedness of the recipient to the actor, B is the benefit gained by the recipient, and C is the cost to the actor
Inclusive fitness - the sum of direct fitness (the individual’s fitness) and indirect fitness (impact on fitness of social partners) weighted by the relatedness between the actor and the recipient
Labile - tending to alter quickly and spontaneously
Male-biased - the overrepresentation of males in a given population
Nested alliance - an alliance within an alliance
Reciprocal altruism - a form of altruism in which one organism provides a benefit to another and expects the benefit to be returned in the future
Second-order alliance - an alliance consisting of males in first-order alliances working together to steal females from other alliances or to defend their own females
Triadic interaction - interactions that occur in a group of three (A, B and C) where individuals attempt to band against an individual in the alliance (e. g. A and B versus C)
References
Acevedo-Gutierrez A. Aerial Behavior Is Not a Social Facilitator in Bottlenose Dolphins Hunting in Small Groups. J Mammology (1999) 80:768-776.
Brager et al. Association patterns of bottlenose dolphins in Galveston Bay, Texas. J Mammology (1994) 75:431-437.
Connor R. Dolphin social intelligence: complex alliance relationships in bottlenose dolphins and a consideration of selective environments for extreme brain size evolution in mammals. Phil. Trans. Soc. B (2007).
Connor et al. Patterns of female attractiveness in Indian Ocean bottlenose dolphins. Behaviour (1996) 133:37-69.
Connor et al. Super-alliance of bottlenose dolphins. Nature (1999) 397:571-572.
Connor R, Heithaus M, Barre L. Complex social structure, alliance stability, and mating success in a bottlenose dolphin ‘super-alliance.’ Proc. R. Soc. Lond. B (2001) 268:263-267.
Connor R, Krutzen M. 2003. Case Study 4B: levels and patterns in dolphin alliance formation. In: Waal F, Tyack P. Animal Social Complexity. USA: Harvard University. 115-120.
Connor R, Mann J, Watson-Capps J. A sex-specific affiliative contact behavior in Indian Ocean Bottlenose dolphins, Tursiops sp. Ethology (2006) 112:631-638.
Connor R, Norris K. Are dolphins reciprocal altruists? Am. Nat. (1982) 119:358-374.
Connor R, Smolker R, Bejder L. Synchrony, social behaviour and alliance affiliation Indian Ocean bottlenose dolphins, Tursiops aduncus. Animal Behavior (2006) In press.
Connor R, Smolker R, Richards A. Two levels of alliance formation among male bottlenose dolphins (Tursiops sp.). Proc. Natl. Acad. Sci. USA (1992) 89:987-990.
Connor R, Smolker R. ‘Pop’ goes the dolphin: a vocalization male dolphins produce during consortships. Behaviour (1996) 133:643-662.
Connor R, Whitehead H. Alliance II. Rates of encounter during resource utilization: a general model of intrasexual alliance formation in fission-fusion societies. Animal Behaviour (2005) 69:127-132.
Conradt L, Roper T. Activity synchrony and social cohesion: a fission-fusion model. Proc. R. Soc. Lond. B (2000) 267:2213-2218.
Duffield D, Wells R. The combined application of chromosome, protein and molecular data for the investigation of social unit structure and dynamics in Tursiops truncatus. Intl. Whaling Comm. (1991) 13: 155-169.
Gero et al. Behaviourally specific preferred associations in bottlenose dolphins, Tursiops sp. Can. J. Zool. (2005) 83:1566-1573.
Gibson Q, Mann J. Early social development in wild bottlenose dolphins: sex differences, individual variation and maternal influence. Animal Behaviour (2008) 76:375-387.
Gibson Q, Mann J. The size, composition and function of wild bottlenose dolphin (Tursiops sp.) mother-calf groups in Shark Bay, Australia. Animal Behavior (2008) 76:389-405.
Gunter G. Contributions to the Natural History of the Bottlenose Dolphin, Tursiops Truncatus
(Montague), on the Texas Coast, with Particular Reference to Food Habits. J. Mammology (1943) 23: 267-276.
Hamilton, W. D. The genetical evolution of social behavior. J Theor Biol. (1964) 1:1-16.
Krutzen et al. Contrasting relatedness patterns in bottlenose dolphins (Tursiops sp.) with different alliance strategies. Proc. R. Soc. Lond. B (2003) 270:497-502.
Krutzen et al. ‘O father: where art thou?’ — Paternity assessment in an open fission–fusion society of wild bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia. Molecular Ecology (2004) doi: 10.1111/j.1365-294X.2004.02192.x.
Lusseau D. Why are male social relationships complex in the doubtful sounds bottlenose dolphin population? PLoS ONE (2007) 4:1-8.
Mann et al. Female reproductive success in bottlenose dolphins (Tursiops sp.): life history, habitat, provisioning, and group-size effects. Behavioral Ecology (2000) 11:210-219.
Mann J, Smuts B. Behavioral development in wild bottlenose dophin newborns (Tursiops sp.). Behavior (1999) 136:529-566.
Mann J, Smuts, B. Natal attraction: allomaternal care and mother-infant separations in wild bottlenose dolphins. Animal Behaviour (1998) 55: 1097-1113.
Marino et al. Cetaceans have complex brains for complex cognition. PLoS Biology (2007) 5:966-972.
Moller et al. Alliance membership and kinship in wild male bottlenose dolphins (Tursiops aduncus) of southeastern Australia. Proc. R. Soc. Lond. B (2001) 268:1941-1947.
Nishida, T. Alpha Status and Agonistic Alliance in Wild Chimpanzees. Primates (1983) 24: 313-336.
Packer C, Pusey A. Cooperation and competition within coalitions of male lions: kin selection or game theory? Nature (1982) 296:740-742.
Parsons et al. Kinship as a basis for alliance formation between male bottlenose dolphins, Tursiops truncates, in the Bahamas. Animal Behaviour (2003) 66:185-194.
Scott et al. Aggression in bottlenose dolphins: evidence for sexual coercion, male-male competition, and female tolerance through analysis of tooth-rake marks and behaviour. Behaviour (2005) 142:21-44.
Smolker et al. Sex differences in patterns of association among Indian Ocean bottlenose dolphins. Behaviour (1992) 123:1-2.
Smolker R, Pepper J W. Whistle convergence among allied male bottlenose dolphins (Delphinidae, Tursiops sp.). Ethology (1999) 105:595-618.
Trivers, R. The Evolution of Reciprocal Altruism. The Quarterly Review of Biology (1971) 46:1-35.
Whitehead H, Connor R. Alliance I. How large should alliances be? Animal Behaviour (2005) 69:117-126.
About the author
I am a sophomore Biochemistry and Cell Biology major from Dallas, TX. I enjoy drawing, painting, baking, and spending time with friends. In studying animal behavior, I am fascinated by learning about the motivation of organisms to behave in certain ways and how seemingly different behavior can be driven by similar principles. Most of the time, studying animal behavior proved easy mostly because it is interesting and applicable. I found myself often trying to relate what we learned in class to humans and trying to observe certain behaviors in my friends and myself.
